Can You Fail a Drug Test from Secondhand Smoke? Understanding the Facts Second hand vaping exposure very low compared to second hand smoking UCL News UCL University College London Thirdhand Smoke Resource Center Protecting Californians Even if an employee only uses marijuana on the weekends, it could still show up on their workplace sponsored drug screen the following week or later. According to some estimates, traces of THC Air Force says CBD products not ok to use, may cause positive drug test > Air Combat Command > Article Display